Can you build your own uninterruptible power supply with a car battery, an inverter, and a battery charger?

Question

The point is to create a UPS with a very long run time when the main power goes out.

Can you hook the charger to the car battery terminals and then attach an inverter to the same terminals (in parallel they call it?). You then plug your computer or whatever to the inverter.

The whole setup would have to automatic. For instance, the charger can sense when the battery is fully charged and turn itself off automatically. With the setup, you shouldn't have to plug or unplug things manually based on what you're doing. It should be automatic, transparent, and operate in the background like any UPS.

Is this at all possible, or is it much more complex to get something like this working? Is this a fire or electrocution hazard? Will the equipment burn out the moment you hook everything together?

Answer 1

A battery charger that will do what you want will cost a very pretty penny. I would stick with the toys that are made to do that. And I agree with the posting above. A car battery has thin lead plates and would not hold up very long at all to the task.

Read this link, it will tell you how to do it just don't put the solar panels or charge controller on it. It is all in the Inverter.

http://www.oynot.com/solar-power.html

Buy this kind of batteries Deep Cycle.

http://store.oynot.com/concorde-sun-xtender-batteries.html

Get one of these types of inverters because most modified sine wave inverters are cheapies and will not allow a power strip or a desktop computer because they use a neutral ground. This makes the inverter switch off till the ground is removed. These work great. And they are true sine wave like normal house electric. Modified sine wave inverters will make motors hammer and shorten their lifes. Some make radios and TV sets buzz. I said some not all. There are some high grade modified sinewave inverters but if paying that much money may as well get a good one with a built in battery charger.

http://store.oynot.com/statpower-prosine.html

But it is going to cost a little cash. I have a backup electric system setup but it is solar powered.

Answer 2

You can do it like that, but it would cost more than buying a UPS. You would need to buy a modified sine wave inverter (expensive) which is different than the ones you get at Wal Mart or a truckstop. The automatic battery charger would be expensive, and I would use a deep cycle (marine) battery for longer service time and longer life. You will also need everything properly fused. You are looking at $400 at a minimum for the proper setup.

Answer 3

It would probably work, but you've got to remember that car batteries produce hydrogen gas when they charge. I would hate for you to blow up your new creation and part of your house from an errant spark. Plus, all the battery chargers that I have ever used produced an irritating hum. If you can deal with those two problems, then kudos, and long live your UPS.